Increase of carbamylcholine-induced 22Na+ influx into pheochromocytoma PC12h cells by nerve growth factor.

Carbamylcholine (CCh)-induced 22Na+ influx into clonal rat pheochromocytoma PC12h cells increased remarkably by culturing the cells in the presence of nerve growth factor (NGF) at a concentration of 50 ng/ml. After 2-4 days in culture with NGF, the CCh-induced 22Na+ influx into cells was enhanced 3- to 5-fold compared to the influx into NGF-untreated cells. No increase of CCh-induced 22Na+ influx was seen prior to 15 h. The ED50 value for NGF to increase the responsiveness was 4.6 ng/ml. This effect could not be mimicked by the addition of 1 mM dibutyryl cyclic AMP. Besides NGF, epidermal growth factor increased the CCh-induced 22Na+ influx into cells to a lower extent that NGF did. Insulin and dexamethasone had no effect. By contrast, the amount of [125I] alpha-bungarotoxin binding to PC12h cells was not changed when cultured in the presence of NGF. It is concluded that the functional nAChR and alpha-bungarotoxin binding sites of PC12h cells are controlled by different mechanisms.